models: move html_data_attributes to policies.

Move html_data_attributes definitions from models to policies. Which
attributes are permitted as data-* attributes is a view level concern
and should be defined on the policy level, not the model level. Models
should be agnostic about how they're used in views.

app/policies/user_feedback_policy.rb

@@ -22,4 +22,8 @@ class UserFeedbackPolicy < ApplicationPolicy
   def permitted_attributes_for_update
     [:body, :category, :is_deleted]
   end
+
+  def html_data_attributes
+    super + [:category]
+  end
 end